Increase in gastro cases linked to raw oysters

12 November 2021

Vulnerable South Australians are reminded to avoid eating uncooked oysters after dozens of food-related illnesses linked to the consumption of raw oysters were reported in the past two months.

SA Health’s Acting Director of Food and Controlled Drugs Branch, Joanne Cammans, said 36 cases of Vibrio parahaemolyticus infections linked to eating raw oysters have been notified since September 2021, compared to no cases in 2020 and eight cases in 2019.

“This increase in cases reported to us in such a short period of time is very concerning, as food-borne illnesses can be quite serious for more vulnerable people in our community, such as older South Australians, pregnant people and people  with compromised immune systems,” Ms Cammans said.

“People with lowered gastric acidity, such as those who are taking antacids, and people with liver disease are particularly vulnerable to Vibrio parahaemolyticus and so should avoid eating raw oysters.

“Food borne Vibrio parahaemolyticus infection causes symptoms of gastro, including watery diarrhoea, abdominal cramps, nausea, vomiting, fever and headache, and usually occurs within 24 hours of eating the contaminated food.

“The infection can be acquired by eating undercooked shellfish and fish however raw oysters are often the most common cause.”

Executive Director, Biosecurity at the Department of Primary Industries and Regions (PIRSA), Nathan Rhodes, said the department was working closely with industry to ensure best practice management tools were available and being utilised.

“The number of cases can vary substantially from year to year, and it is difficult to pinpoint the potential cause,” Mr Rhodes said.

“We are looking at potential factors that may have an influence on the recent cases, but the best international science has yet to determine a likely cause. Inspections by PIRSA officers have found that food safety practices are being appropriately applied on farm.

“Raw unshucked oysters, should be stored at less than 10°C and shucked oysters at less than 5°C to minimise the risk of Vibrio parahaemolyticus infection.”

Seafood eaten raw or ready-to-eat cold cooked prawns or cold smoked salmon, are not recommended for pregnant people, people with reduced immune systems or older people because of the risk of bacterial infections such as Vibrio parahaemolyticus.

For more information on food safety, visit www.sahealth.sa.gov.au/foodsafety.